Tire treads having large features such as large block sculptures with large grooves in between are frequently used on heavy vehicles that will travel off road such as e.g., military vehicles. The large blocks are associated by purchasers and users with toughness, durability, and/or improved traction in soft soils or mud. By way of example, tread blocks of size 90 mm by 80 mm and larger have been used in certain military applications.
As purchasers and users increase the weight placed on such tires by e.g., changes in vehicle design, the stress and strains experienced by such tires also increase, Such stress and strains generate heat in the materials of the tire that can be deleterious to the life of the tire, particularly the tread. More particularly, as the materials heat up they can also experience thermal wear in that the materials begin to degrade depending upon e.g., the magnitude the stress and strain and the time period over which such is maintained by operation of the tire.
The thermal wear problem increases with increasing speed. As speed increases, the frequency of the tire's cycle of rotation through the contact patch increases. This increased frequency in turn leads to repeated stress and strain that increases the temperature and thermal wear.
One approach to reducing such thermal wear is to provide a speed limitation for the use of the tire based upon the loading of the tire. For example, a tire might have a limitation of 90 kph for load of 5600 kilograms on the tire. Different limitations might apply based upon the loading of the tire, the design of the tire, and other factors affecting thermal wear. However, for some applications, a speed limitation may not be practical. The applications for the vehicle may require operation at higher speeds. In addition, drivers may not be willing to limit their speed as required.
Other solutions that have been attempted include reducing the size of the tread blocks, using lower hysteresis materials, using a thinner architecture, and still others as well. These approaches, however, may not be available for some applications. For example, reducing the depth of the tread may be unacceptable to some purchasers because of the perceived impact of a shallower tread depth on e.g., off-road traction. Lower hysteresis materials may increase expense or come at a trade-off with other desired properties.
Accordingly, a tire having features that provide improvements in thermal wear would be useful. More specifically, a tire having tread features that provide for reducing strains and/or stresses within the tread so as to reduce thermal wear would be very beneficial. Such tread features that can be readily implemented in existing tire designs and tread constructions would also be useful.